Grinding rubber strips



Aug. 16, 1955 J. A. DORNER 2,715,300

GRINDING RUBBER STRIPS Filed Dec. 14, 1950 ru\\\\\\\\\v 0 35 United States Patent Gfilice Zfililibil Aug. 16, 1955 GRENDENG RUBBER STRIPS John A. Dorner, Akron, Ghio, assignor to The B. F. Goodrich Company, New York, N. Y., a corporation of New York Application December 14, 1956, Serial No. 200,830

3 Claims. (Cl. 511i)5) This invention relates to grinding rubber sealing strips and is particularly useful in grinding the face of rubber strips used in hydraulic devices such as airplane wheel brakes.

In the manufacture of airplane wheel brakes of the hydraulically-operated type, it has been proposed to employ a sealing strip of elongate dumbbell form cupped at one face, the cupped surface being defined by an outwardly flared marginal border terminating in sharp sealing lips. Such strips have presented diificulties in manufacture as it has been found that the strips cannot successfully be produced merely by molding, and grinding of the face of the strip has been difiicult because of the tendency of the strip to lift against the grinding wheel and to be ground where not desired.

It is an object of the present invention to overcome the foregoing and other difficulties.

Other objects are to provide for seating the strip by differential air pressure, to provide for grinding the strip when arranged as an annulus, to provide for reversing the direction of the grinding wheel, and to provide for reversing rotative movement of the work.

These and other objects will appear from the following description and the accompanying drawings.

Of the drawings,

Fig. 1 is a front elevation of apparatus constructed in accordance with and embodying the invention, parts being broken away.

Fig. 2 is a plan view of the chuck thereof, parts being broken away, taken on line 22 of Fig. 1.

Fig. 3 is a cross-sectional view thereof, taken on line 33 of Fig. 2.

Fig. 4 is a cross-sectional view taken on line 4-4 of Fig. 1.

Fig. 5 is a diagrammatic view showing the direction of rotation of the grinding wheel with relation to movement of the strip.

Referring to the drawings, the numeral designates a supporting frame on which a rotatable table 11 is mounted for rotation about a vertical axis. The table is driven through suitable reducing gearing by a sprocket 12 which is in turn driven from a reversible motor 13 through a sprocket 14 and chain 15. A lever 16 is mounted on a rock shaft 17 operating a reversing switch (not shown) controlling the motor 13. The arrangement is such that the table 11 may be rotated in either direction at the will of the operator by shifting the lever 16 in the corresponding direction.

For mounting the strip to be ground on the table 11, a chuck comprising superimposed plates 18, 19 is mounted thereon. The lower plate 18 has an annular groove 20 in its upper face connected to a central opening 21 by radiating grooves 22. A suction pipe 23 is secured in the opening 21 and is connected by a rotary joint 24 to a stationary pipe 25 connected to a vacuum pump (not shown).

The upper plate 19 has a groove formed in its upper face for seating the strip 31, the groove 30 corresponding in cross section to that of the strip with the strip projecting slightly above the plate. The strip 31 is of dumbbell shape having a narrow elongate portion 32 connecting widened ends 33, 34 and the groove 30 is correspondingly shaped in cross section and extends annularly of the chuck with its ends in widely spaced apart relation as shown in Fig. 2. A series of closely spaced vent holes 35 extend through the upper chuck plate 19 and connect the groove 36 with the groove 26 to conduct air from the groove 36. The arrangement is such that when a strip 31 is placed in groove 30 it is held therein by vacuum or differential pressure during rotation of the table.

For grinding the upper or exposed surface of the strip 31, a rail or guideway 41) extends horizontally above the table 11 and is supported by the frame 10. A carriage 41 is slideably mounted on the guideway. A feed screw 42 extends lengthwise of the guideway and is rotatably mounted in a bearing Stop collars 44, 45 at the sides of the bearing prevent axial movement of the screw. A

. handle 4+5 is provided at the end of the screw 42 and is fixed thereto. The screw engages a nut (not shown) secured to carriage 41. The arrangement is such that the screw may be rotated by the handle 46 to move the carriage 41 along the guideway 40. Carriage 41 is formed with a vertical guideway 47 in which a carriage 43 is slideably mounted. A vertical feed screw 49 is journaled in the carriage 41 and has threaded engagement with carriage 48. A handle 50 is fixed to the screw 49. A graduated collar 51 is clamped to the screw to indicate the elevation of the carriage. A reversible electric motor 52 is mounted on carriage 48. A grinding wheel 53 is secured to the shaft 54 of the motor for rotation in either direction, the wheel being secured by a nut 55 threaded on the motor shaft and pinned to prevent loosening when the motor is reversed. A hand-operated switch 56 is provided on the motor for reversing the motor and starting and stopping it. The arrangement is such that both the direction of travel of the work and direction of travel of the wheel may be reversed and the wheel may be raised and returned to the same elevation above the table.

I have found that when it is attempted to grind the face of a rubber strip by movement of the strip lengthwise in either direction and with the wheel running toward a leading end of the strip as the strip approaches the wheel, the leading end of the strip is lifted by the wheel to an extent causing damage to the strip by grinding too much material therefrom while the trailing end of the strip is not damaged. The friction of the wheel is suflicient even with a very light cut to lift the flared end from its groove. To overcome this difliculty the wheel and table are both provided with reversible drives and the work is so ground as to minimize lifting tendency.

Also for this purpose the ends 33, 3d of the strip are spaced well apart to prevent undesirable contact of the wheel with an end of the strip when the wheel is running in a direction toward such end.

As shown in Fig. 5 when the wheel is rotating in a direction relative to end 33 as indicated by the arrow A the end 33 is not lifted. The forces on the portions of the strip adjacent end 33 produced by the abrasive action of the wheel as it rotates in this direction tend to urge the end 33 firmly against the end of the groove 39 in which it is supported, thus preventing the strip from being displaced. With the wheel so rotating the table 11 may be moved to shift the strip lengthwise to move the end 33 and adjacent portions of the strip back and forth (see arrow B) under the wheel until these portions are ground to the desired thickness. Only end 33, however, is ground with the wheel rotating in the direction of arrow A because this rotational direction against end 34 would result in displacement of the end 34 from the groove. Therefore before end 34 is brought under the wheel the rotational direction of the wheel is reversed from that shown in Fig. 5, so that as end 34 is ground it will also be urged against the end of the groove 30 in V which it is located. In other Words, I have found that when the ends of the strip are in the region of contact of the grinding wheel, the wheel should be running in a direction such that the wheel will tend to urge each end of the strip against its respective end of the groove 30 in which it is supported. The tendency for a strip to lift is probably more pronounced where the strip, as in the example shown, has outwardly flared walls. With the walls outwardly flared, the corresponding taper of the supporting groove provides for support of the side walls of, the strip close to the face of the strip being ground which assists in supporting the strip against deflection when the grinding wheel is running toward the end of the strip.

Lifting of the strip is also especially objectionable where, as here, the strip is held in the groove by vacuum as lifting of the end of the strip might break the vacuum resulting in loosening of the strip.

In grinding the surface of the strip, the strip is laid in the groove of the chuck and the pipe 25 is connected to an air pump which provides a vacuum to seat the strip.

The motor 52 is started to cause the grinding Wheel to rotate relative to end 33 as shown in Fig. 5, for example. The grinding Wheel is lowered to contact the face of the strip and the table is rotated to a position where the wheel contacts a portion of the strip intermediate ends 33 and 34 and preferably at about the midpoint between the ends 33 and 34. The table is then rotated in a direction such as to cause the said end 33 of the strip to approach the wheel to grind an arc of the strip including said end. The wheel is lowered and the table rotated back and forth through such are until'the correct depth is reached as indicated on the graduations 51. The wheel is then raised and its direction reversed. With the Wheel running in the reverse direction, the unground arc of the strip is ground by rotating the table back'and forth through the remaining arc.

As the grinding wheel travels at a relatively high surface speed while movement of the chuck is relatively slow, the resulting force due to the sum or difference of the velocities is directed toward the end of the groove in which the strip is held regardless of direction of rotation of the chuck or movement of the strip as long as the grinding wheel is rotated in that direction. Therefore, the grinding wheel must always be rotated to urge the ends of the strip toward their respective ends of the groove when contacting the strip at such end.

Variations may be made without departing from the scope of the invention as it is defined by the following claims.

I claim:

1. Apparatus for grinding the margins of a cupped face of an extensive strip of soft rubber material, said apparatus comprising a rotatable table having an annular concentric groove in its face for seating the strip therein with its cupped face exposed, the groove being arranged to support the sides and ends of the strip against deflection-with the .ends of the strip spaced from each other,

means for rotating the table in opposite directions, vacuum producing means connected to said groove for holding the strip in said groove, a rotatable grinding wheel adjacent the groove of said table, means for feeding said grinding wheel into contact with said strip, and means for driving the grinding wheel in one direction for grinding the face of the strip from a portion intermediate the ends of the strip toward one end of the strip and in the opposite direction for grinding the face of the strip from said intermediate portion of the strip towardthe opposite end of the strip while said ends are supported by the ends of the groove against lifting or deflection.

2. Apparatus for grinding a face of an extensive strip of rubber material, said apparatus comprising a rotatable table having an annular groove concentric therewith for seating the strip therein and supporting the sides and ends of the strip with the ends of the strip in spaced-apart relation, means for rotating said table in opposite directions, means for evacuating said groove during rotational movement of said table to hold the strip in place, a grind ing wheel mounted in the path of movement of said table, means for driving said grinding wheel, and means for reversing the direction of rotation of said wheel to efiect rotation of the wheel toward one end of the strip when the wheel is in a position intermediate the ends of the strip while the table is rotated simultaneously to advance the opposite end past the wheel and to rotate said wheel in the reverse direction when said table is rotated in the opposite direction to advance the first said end of the strip past the grinding wheel.

3. Apparatus for grinding a face of an extensive strip of rubber material, said apparatus comprising a table, supporting means for the table, means for rotating the table relative to said supporting means in reverse directions, a groove disposed generally concentrically about the rotational axis of the table for seating the strip and supporting the ends of the strip against displacement in a direction lengthwise of the strip, means for retaining the strip in the groove, a grinding Wheel adjustably supported for movement toward and away from the table, the table being rotatable to move the strip lengthwise relative to the grinding wheel, means for rotating the grinding wheel in a first direction when grinding adjacent one end of the strip, and means for rotating the grinding wheel in the reverse direction when grinding the opposite end of the strip, and the rotational direction of the wheel at each of said ends of the strip being such that each end of the strip is urged by the wheel against the respective end of the groove in which it is located to prevent displacement of the strip.

References Cited in the file of this patent UNITED STATES PATENTS 684,547 Hibbard Oct. 15, 1901 719,297 Van Berkel Ian. 27, 1903 985,412 Hattersley et al Feb. 28, 1911 1,971,582 Scruby Aug. 28, 1934 2,323,744 Wikle July 6, 1943 2,367,839 Grover Jan. 23, 1945 2,402,305 Sutton June 18, 1946 2,405,417 Fruth Aug. 6, 1946 

